The subject of bleeding was briefly addressed in the first edition of ASTM STP 169, published in 1956. Ivan L. Tyler, manager of the Field Research Section of the Portland Cement Association, concisely described the general significance of tests for bleeding in his article on Uniformity, Segregation, and Bleeding in the Freshly Mixed Concrete section of ASTM STP 169. ASTM STP 169A and ASTM STP 169B did not address bleeding. This chapter elaborates on fundamental concepts presented by Mr. Tyler. The effects of concrete ingredients on bleeding as well as the significance of bleeding with modern concretes are presented. The chapter also reviews the standard ASTM test methods on bleeding and provides data on the bleeding characteristics of a variety of cement pastes, mortars, and concretes.